Method and equipment for assessing the life of members put under high in-service temperature environment for long period

ABSTRACT

For each component which is used at a high in-service temperature for a long period, its creep damage degree is approximated by a relational expression containing the Larson-Miller parameter. The creep damage degree is estimated by an approximation expression obtained by determining constants for each component. The creep damage degree is subjected to Weibull statistical analysis to estimate the creep damage degree probabilistically. Also, the thermal fatigue and damage degree obtained by an approximation expression is likewise subjected to Weibull statistical analysis to estimate the thermal fatigue and damage degree probabilistically. Therefore, the probabilistically estimated creep damage degree and the probabilistically estimated thermal fatigue and damage degree allows the life of each component subjected to a high in-service temperature to be assessed precisely and quickly.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Applications No. 2000-114126, filed Apr.14, 2000; and No. 2001-006859, filed Jan. 15, 2001, the entire contentsof both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a method and equipment forassessing the duration of life of members put under a high in-servicetemperature environment for a long period and more specifically to amethod and equipment for assessing the duration of life of each memberput under a high in-service temperature environment for a long period,for example, the high or intermediate pressure rotor, the high orintermediate pressure casing, and the main stop valve, that areincorporated into a steam turbine unit.

[0003] Conventionally, a member which is put under a high in-servicetemperature environment for a long period, for example, the rotor in asteam turbine unit, is subjected continuously to a load for a longperiod in a high in-service temperature environment and hence sufferscreep damage; as a consequence, its duration of life is reduced. Also,the rotor is repeatedly subjected to thermal stresses at the times ofstarting and stopping the turbine, resulting in the reduced duration oflife. To ensure the reliability of the steam turbine unit over a longperiod, therefore, it is important to assess the duration of life of itsstructural members with precision.

[0004] Heretofore, as a technique to assess the life of such members,one has been developed and put to practical use which involvessubjecting virgin materials for new components and used materials ofcomponents which have been put at high in-service temperatures and areto be scrapped at the time of replacement to a destructive test andassessing their residual life on the basis of the materialcharacteristic test results. That is, in the destructive test, the creeprupture strength and the low-cycle fatigue strength of those materialsare obtained on a laboratory basis. The creep rupture strength and thelow-cycle fatigue strength are obtained as a function of a certainparameter, for example, a function of hardness. In inspecting a steamturbine unit regularly, the hardness of the individual members ismeasured as their intrinsic parameter. From the intrinsic parameters ofthe individual members, i.e., the creep rupture strength and low-cyclefatigue strength data as a function of hardness, the operation historyof the unit and its residual life allowing for future operation areassessed.

[0005] An example of a technique to assess the residual life is onedisclosed in Jpn. Pat. Appln. KOKAI No. 1-27378. The technique ofresidual life assessment disclosed in this publication involvescalculating the temperature-stress characteristic of a structural membersubjected to a high in-service temperature from its working conditionvalue, calculating the material characteristic of the structural memberfrom its hardness, calculating the damage cumulative value of thestructural member by adding corrections corresponding to the operationhistory to these characteristics by condition setup equipment, andcomparing the damage cumulative value with an allowable value. It issaid that such a technique can predict accurately the time when a crackis initiated in the structural member.

[0006] Conventionally, the life of individual members is obtained foreach unit. In this life assessment, the creep damage and the thermalfatigue damage or low-cycle fatigue damage are obtained by linearcumulative damage rules and a method to assess the residual lifeallowing for future operation is adopted. Thus, the conventionalmethods, which assess the residual life for each unit or for each memberin each unit, can produce variations in assessment and cannot makeassessment quickly. From this point of view, the development of atechnique to assess the residual life of structural members preciselyand quickly has been demanded in recent years.

[0007] Conventionally, in assessing the life of a member in a turbine orthe like, its hardness is measured at regular inspection (in-serviceinspection) time and the life is assessed utilizing the measuredhardness. Unless the hardness is measured at regular inspection time,life assessment cannot be made with precision. It is difficult tomeasure the hardness at any desired time.

[0008] To ensure precise and quick life assessment, a method is requiredwhich collects changes with time in the hardness of each individualmember and stochastically estimates the hardness of a member in aturbine or the like to thereby assess its life.

BRIEF SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide a method andequipment which permit the life of a structural member put under a highin-service temperature environment to be assessed precisely and quickly.

[0010] It is another object of the present invention to provide a methodand equipment which, by collecting changes with time in the hardness ofeach individual member put under a high in-service temperatureenvironment, permits its hardness to be estimated stochastically and itslife to be assessed precisely and quickly.

[0011] According to an aspect of the present invention, there isprovided a method of assessing the life of a member subjected to a highin-service temperature for a long period comprising the steps of:

[0012] determining a Larson-Miller parameter for the member whose lifeis to be assessed from the in-service temperature and a service timeperiod during which the member is used in-service temperature, andcalculating the creep damage degree on the basis of cumulative damagerules from the hardness and stress of the member to establish data; and

[0013] approximating the relationship between the Larson-Millerparameter and the creep damage degree by an expression including anexponential function.

[0014] According to an aspect of the present invention there is alsoprovided a method of assessing the life of a member subjected to a highin-service temperature for a long period comprising the steps of:

[0015] determining a Larson-Miller parameter for the member whose lifeis to be assessed from the in-service temperature and service timeperiod during which the member is used in-service temperature and usingdata established by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member toapproximate the relationship between the Larson-Miller parameter and thecreep damage degree by an expression including an exponential function;and

[0016] estimating the creep damage degree by adding probabilisticstatistical processing to the approximate expression.

[0017] Furthermore, according to an aspect of the present inventionthere is provided a method of assessing the life of a member provided inan apparatus which is started and stopped over and over again andsubjected to a high in-service temperature for a long period while theapparatus is being operated comprising the steps of:

[0018] calculating an estimation parameter which is a function of a setof the start count and thermal stress, and thermal fatigue and damagedegree based on cumulative damage rules for the member whose life is tobe assessed and establishing data; and

[0019] approximating the relationship between the estimation parameterand the thermal fatigue and damage degree by an approximate expression.

[0020] According to an another aspect of the present invention, there isalso provided an apparatus for assessing the life of a member subjectedto a high in-service temperature for a long period, comprising:

[0021] means for determining a Larson-Miller parameter for the memberwhose life is to be assessed from the in-service temperature and aservice time period during which the member is used in-servicetemperature, and calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member toestablish data; and

[0022] means for approximating the relationship between theLarson-Miller parameter and the creep damage degree by an expressionincluding an exponential function.

[0023] According to an yet another aspect of the present invention,there is also provided an n apparatus for assessing the life of a membersubjected to a high in-service temperature for a long period comprising:

[0024] means for determining a Larson-Miller parameter for the memberwhose life is to be assessed from the in-service temperature and servicetime period during which the member is used in-service temperature andusing data established by calculating the creep damage degree on thebasis of cumulative damage rules from the hardness and stress of themember to approximate the relationship between the Larson-Millerparameter and the creep damage degree by an expression including anexponential function; and

[0025] means for estimating the creep damage degree by addingprobabilistic statistical processing to the approximate expression.

[0026] Furthermore, according to a yet another aspect of the presentinvention, there is provided an apparatus for assessing the life of amember provided in an apparatus which is started and stopped over andover again and subjected to a high in-service temperature for a longperiod while the apparatus is being operated comprising:

[0027] means for calculating an estimation parameter which is a functionof a set of the start count and thermal stress, and thermal fatigue anddamage degree based on cumulative damage rules for the member whose lifeis to be assessed and establishing data; and

[0028] means for approximating the relationship between the estimationparameter and the thermal fatigue and damage degree by an approximateexpression.

[0029] Furthermore, according to a yet further aspect of the presentinvention, there is also provided an apparatus for assessing the life ofa member provided in an apparatus which is started and stopped over andover again and subjected to a high in-service temperature for a longperiod while the apparatus is being operated comprising:

[0030] means for using an estimation parameter which is a function ofthe start count and thermal stress, and data established by calculatingthermal fatigue and damage degree based on cumulative damage rules, forthe member whose life is to be assessed, and approximating therelationship between the estimation parameter and the thermal fatigueand damage degree by an approximate expression; and

[0031] means for estimating the thermal fatigue and damage degree byadding probabilistic statistical processing to this approximateexpression.

[0032] Furthermore, according to a yet another aspect of the presentinvention, there is provided a method of assessing the life of a membersubjected to a high in-service temperature for a long period comprisingthe steps of:

[0033] determining a Larson-Miller parameter for the member whose lifeis to be assessed from the in-service temperature and time of the memberand using data established by calculating the creep damage degree on thebasis of cumulative damage rules from the hardness and stress of themember to approximate the relationship between the Larson-Millerparameter and the creep damage degree by an expression including anexponential function;

[0034] prompting a terminal connected through a network to input thein-service time period, of the member whose life is to be assessed;

[0035] assessing the life of the member from the in-service time period,of the member whose life is to be assessed by using the approximateexpression; and

[0036] outputting the assessed life to the terminal.

[0037] According to a yet further aspect of the present invention, thereis provided an apparatus for assessing the life of a member subjected toa high in-service temperature for a long period comprising:

[0038] means for determining a Larson-Miller parameter for the memberwhose life is to be assessed from the in-service temperature and time ofthe member and using data established by calculating the creep damagedegree on the basis of cumulative damage rules from the hardness andstress of the member to approximate the relationship between theLarson-Miller parameter and the creep damage degree by an expressionincluding an exponential function;

[0039] means for prompting a terminal connected through a network toinput the in-service time period, of the member whose life is to beassessed;

[0040] means for assessing the life of the member from the in-servicetime period, of the member whose life is to be assessed by using theapproximate expression; and

[0041] means for outputting the assessed life to the terminal.

[0042] According to a yet further aspect of the invention, there isprovided an apparatus for assessing the life of a member subjected to ahigh in-service temperature for a long period comprising:

[0043] means for determining a Larson-Miller parameter for the memberwhose life is to be assessed from the in-service temperature and servicetime period during which the member is used in-service temperature andusing data established by calculating the creep damage degree on thebasis of cumulative damage rules from the hardness and stress of themember to approximate the relationship between the Larson-Millerparameter and the creep damage degree by an expression including anexponential function and further to prepare an expression estimating thecreep damage degree added with probabilistic statistical processing;

[0044] means for prompting a terminal connected through a network toinput the in-service time period, and the hardness of the member whoselife is to be assessed;

[0045] means for assessing the life of the member from the in-servicetime period, of the input member; and

[0046] means for outputting the assessed life to the terminal.

[0047] In the above described method and apparatus, the Larson-Millerparameter P is calculated by an expression given as

P=(T+273)(log t+C)

[0048] where C is the material constant, T is the in-service temperatureand t is the in-service time period, and the creep damage degree φcbased upon the cumulative damage rules is calculated by an expressiongiven as

P′=A1(σ)H+B1(σ)

[0049] where σ is the stress, and H is the hardness,

P′=(T+273)(log tr+C)

[0050] where C is the material constant, T is the in-servicetemperature, and tr is creep rupture life,

φc=t/(tr+t) or φc=t/tr

[0051] where φc is the creep damage degree, and

[0052] where, when data of the hardness of the portion under a highin-service temperature and a high stress of the member whose life is tobe assessed is used, φc=t/(tr+t) is employed, and when data of thehardness of the portion under a high in-service temperature and a lowstress is used to assess the portion of the member under a highin-service temperature and a high stress, φc=t/tr is employed.

[0053] In the above described method and apparatus, the creep damagedegree φc is obtained by

φc=1−exp(A·P ^(B))

[0054] wherein A and B are constants and P is the Larson-Millerparameter.

[0055] In the above described method and apparatus, the creep damagedegree where the probabilistic statistical processing is added to theapproximate expression is also estimated by an expression given as

φc={1−exp(A·P ^(B))}·{β·^(m){square root}{square root over(ln(1−Pf)⁻¹)}}

[0056] where m is the Weibull coefficient, β is the scale parameter, andPf is the cumulative probability.

[0057] the cumulative probability Pf corresponds to the cumulativeprobability Pf defined by the following expression and the cumulativeprobability Pf depending on the hardness is obtained by an expressiongiven as

Pf=1−exp{−(μ/β)^(m)}

[0058] where m is the Weibull coefficient, β is the scale parameter, andμ is the hardness of the member (experimental value)/the hardness of themember (estimated value), and

[0059] further the estimated value of the hardness of the member isobtained by an equation using the least squares method given as

at+b,

[0060] where t is the total operation time when the hardness of themember is measured, and a and b are constants.

[0061] In the above described method and apparatus, the hardness of themember is estimated by a probabilistic expression given as

H=(at+b)(β·^(m){square root}{square root over (ln(1−Pf)⁻¹)})

[0062] wherein H is the hardness of the member, t is the total operationtime when the hardness of the member is measured, a and b are constants,m is the Weibull coefficient, β is the scale parameter, and Pf is thecumulative probability corresponding to the hardness of the member.

[0063] In the above described method and apparatus, the estimationparameter q is given by an expression of

q=N(σc·nc/N+σw·nw/N+σh·nh/N)^(α)

[0064] where α is the constant, σc is the thermal stress of the memberat cold start time, σw is the thermal stress of the member at warm starttime, σh is the thermal stress of the member at hot start time, N is thetotal start count, nc is the cold start count, nw is the warm startcount, and nh is the hot start count, and the thermal fatigue and damagedegree is approximated by an expression given as

φf=C·q

[0065] where Cf is a constant.

[0066] In the above described method and apparatus, the thermal fatigueand damage degree obtained by adding the probabilistic statisticalprocessing to the approximate expression is given by an expression of

φf=Cf·q(β·^(m){square root}{square root over (ln(1−Pf)⁻¹)})

[0067] where m is the Weibull coefficient, β is the scale parameter, andPf is the cumulative probability.

[0068] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0069] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the invention, and together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, serve to explain the principles of the invention.

[0070]FIGS. 1A and 1B are block diagrams of equipment for assessing thelife of a member put under a high in-service temperature environment fora long period based on the creep rapture damage degree in accordancewith an embodiment of the present invention;

[0071]FIG. 2 is a graph showing a relationship between a creep damagedegree φ and the Larson-Miller parameter P;

[0072]FIGS. 3A and 3B form a block diagram of equipment for assessingthe life of a member put under a high in-service temperature environmentfor a long period based on the thermal fatigue and damage degree inaccordance with another embodiment of the present invention;

[0073]FIG. 4 is graph showing a relation ship between a thermal fatigueand damage degree φf and estimation parameter of the thermal fatigue anddamage degree q;

[0074]FIGS. 5A to 5C form a block diagram illustrating a more specificembodiment of equipment for assessing the life of a member put under ahigh in-service temperature environment for a long period in accordancewith the present invention;

[0075]FIG. 6 is a graph showing the results of assessment of thestochastic creep damage degree of a turbine member obtained by steamturbine member's life assessment equipment of the present invention;

[0076]FIG. 7 is a graph showing the results of assessment of thestochastic thermal fatigue and damage degree of a turbine memberobtained by steam turbine member's life assessment equipment of thepresent invention;

[0077]FIG. 8 is a block diagram of a modification of the equipment forassessing the life of a member put under a high in-service temperatureenvironment for a long period in accordance with the present invention;

[0078]FIG. 9 is a detailed block diagram of the section for estimatingthe stochastic hardness of the turbine member shown in FIG. 8;

[0079]FIG. 10 is a characteristic diagram showing the relationship ofoperating time and hardness for use in explanation of calculations inthe section for estimating the stochastic hardness of the turbine membershown in FIG. 8;

[0080]FIG. 11 is a characteristic diagram showing variations in data inthe relationship of operating time and hardness for use in explanationof calculations in the estimation of the stochastic hardness of theturbine member shown in FIG. 8;

[0081]FIG. 12 is a block diagram of the section for assessing thethermal fatigue and damage of the turbine member shown in FIG. 8;

[0082]FIG. 13 is a block diagram of the means for assessing the creepdamage of the turbine member shown in FIG. 8; and

[0083]FIG. 14 is a schematic illustration of a system adapted totransmit the results of assessment by the life assessment method andequipment shown in FIG. 8 over the Internet.

DETAILED DESCRIPTION OF THE INVENTION

[0084] Hereinafter, the method and equipment for assessing the life of amember that is put under a high in-service temperature environment for along period, in accordance with the present invention will be describedwith reference to the accompanying drawings.

[0085] The method of life assessment of the invention is generalizedsuch that the creep damage degree and the thermal fatigue and damagedegree of a structural member which is put under a high in-servicetemperature environment for a long period are calculated on the basis ofcumulative damage rules, the calculated creep damage degree and thermalfatigue and damage degree are stored as data in a storage device, andthe residual life of that member is predicted and analyzedprobabilistically using both data on the basis of the Weibullstatistical analysis.

[0086] In this life assessment, the material strength characteristic isestimated from hardness data and its life is predicted based on thosedata, history data, design data.

[0087] Hereinafter, an embodiment of equipment for assessing the life ofa member which is put under a high in-service temperature environmentfor a long period will be described with reference to the drawings.

[0088]FIGS. 1A and 1B are functional block diagrams for use inexplanation of the equipment for assessing the life of a structuralmember used at a high in-service temperature in accordance with thepresent invention. A system that estimates probabilistically the creepdamage degree of a steam turbine member includes functions shown in FIG.1A. That is, the estimation system is composed of an input section 1 forinputting data concerning a member in a steam turbine, a storage section2 for storing the data, a calculation section 3 for calculating thecreep damage degree on the basis of the data, a storage section 4 forstoring the calculated value from the calculation section, and acalculation section 5 for estimating the creep damage degree using acertain approximation expression.

[0089] The data concerning the member in the steam turbine entered intothe data input section 1 include assessed component data, design data,inspection data, and operation history data. The assessed component dataincludes the unit name of a component as the subject of residual lifeassessment, the material name of the component, and the region name ofthe component. The design data includes the temperature T and the stressσ to which the structural member is subjected during the steady-stateoperation of the steam turbine. The inspection data includes thehardness (Vickers hardness) H of the structural member measured at thetime of in-service inspection of the steam turbine. The operationhistory data is the total operation time of the steam turbine.

[0090] The storage section 2 is stored with the assessed component data,the design data, the inspection data, and the operation history datainput from the input section 1 of data relating to the steam turbinemember. Those data are accessed and output when they are needed in thecalculation sections 3 and 5.

[0091] The creep damage degree calculation section 3 calculates thecreep damage degree φc on the basis of pre-stored expressions (1)through (4).

[0092] At the time of steady operation under conditions of a highin-service temperature and a constant stress, creep damage occurs ineach member and its creep rupture dame degree φc can be estimated fromthe hardness H and the stress, i.e., steady-state stress a through theLarson-Miller parameter P′ given by

P′=A1(σ)H+B1(σ)  (1)

[0093] where σ is the stress, H is the Vickers hardness and so on, andA₁ and B₁ are constants.

[0094] On the other hand, the Larson-Miller parameter P′ is represented,as a function of the in-service temperature T(K) and the creep rupturelife tr, by

P′=(T+273)(log tr+C)  (2)

[0095] where C is the material constant.

[0096] Thus, by measuring the hardness H of a member at the time ofin-service inspection of the steam turbine or estimating the hardness ofthe member at a certain point of time as will be described later,knowing the in-service temperature T (K) and the stress σ allows thelife up to the time the member undergoes creep rupture life time orperiod tr to be estimated by

tr=10^({P′/(T+273)−C})  (3)

[0097] where C is the material constant, T is the in-servicetemperature, and tr is creep rupture life,

φc=t/(tr+t) or φc=t/tr  (4)

[0098] where φc is the creep damage degree, and

[0099] where, when data of the hardness of the portion under a highin-service temperature and a high stress of the member whose life is tobe assessed is used, φc=t/(tr+t) is employed, and when data of thehardness of the portion under a high in-service temperature and a lowstress is used to assess the portion of the member under a highin-service temperature and a high stress, φc=t/tr is employed.

[0100] The stored data of the creep damage degree φc has a relationshipwith the Larson-Miller parameter P as shown in FIG. 2, wherein the creepdamage degrees φc are plotted in a relation of the Larson-Millerparameter P.

[0101] The computational results from the calculation section 3 areretained in the storage section 4 where they are stored for each memberand each region. Specifying the name of a member or region allows itsassociated computational results to be accessed. Thus, the calculationresult storage section 4 is stored with combined data of the creepdamage degree φc and the Larson-Miller parameter P for each of manymembers and assessment regions.

[0102] Next, in the creep damage degree estimation approximationexpression calculation section 5, an approximation expression for thecreep damage degree φc is calculated from expression (5) representingthe relationship of the creep damage degree φc and the Larson-Millerparameter P for each assessment region of each component. Theapproximation expression (5) is decided by combined data of the creepdamage degree φc and the Larson-Miller parameter P stored in the storagesection 4 for each assessment region of each individual member. That is,constants A and B in approximation expression (5) are obtained for eachregion of each member. The creep damage degree φc is estimated byapproximation expression (5) representing the relationship of P and φc.

φc=1−exp(A·P ^(B))  (5)

[0103] where A and B are constants.

[0104] Experiments have confirmed that approximation expression (5) isvery close to the relationship of the creep damage degree φc and theLarson-Miller parameter P_measured actually for members of a steamturbine.

[0105] Next, as shown in FIG. 1B, the estimated creep damage degree φcis input from the creep damage degree estimation approximationexpression calculation section 5 to a system that estimates theprobabilistic life. This system is composed of a section 6 for Weibullstatistical processing and a calculation section 7 for a probabilisticestimation expression of the creep damage degree φc.

[0106] In the Weibull statistical processing section 6, the estimatedcreep damage degree φc is subjected to Weibull statistical analysis. Inthe probabilistic estimation expression calculation section 7, theprobabilistic life is predicted from the analyses.

[0107] Variations in data in the relationship of the creep damage degreeφc and the Larson-Miller parameter P as a function of the operation timeperiod t(h) and the in-service temperature T(K) can be closelyapproximated by the Weibull distribution, and the Weibull coefficient mand the scale parameter β are calculated through the Weibull statisticalanalysis.

[0108] The creep damage degree probabilistic estimation expressioncalculation section 7 calculates an expression to estimateprobabilistically the creep damage degree φc as

φc={1−exp(A·P ^(B))}·{β·^(m){square root}{square root over(ln(1−Pf)⁻¹)}}  (6)

[0109]FIGS. 3A and 3B form a block diagram of another embodiment of theequipment for assessing the life of structural members used at a highin-service temperature in accordance with the present invention. In thesystem shown in FIG. 3A, the probabilistic thermal fatigue and damagedegree of a steam turbine member is estimated. This system is composedof a data input section 1A for receiving data concerning a member in asteam turbine, a storage section 2A for storing the input data, acalculation section 8 for calculating the thermal fatigue and damagedegree, a storage section 9 for storing the calculated value from thecalculation section, and a calculation section 10 for determining anapproximation expression for estimating the thermal fatigue and damagedegree.

[0110] The data concerning a member in the steam turbine entered intothe data input section 1A include to-be-assessed component data, designdata, inspection data, and operation history data. The to-be-assessedcomponent data includes the unit name, member name, and member regionname. The design data includes the in-service temperature T and stress σto which a structural member is subjected. Specifically, the stressincludes the cold stress σc at cold start time, for example, at starttime after the in-service inspection of the steam turbine, the warmthermal stress σw at warm start time, for example, at the time of startafter the weekend stoppage, and the hot thermal stress σh at hot starttime, for example, at everyday start time. The inspection data includesthe hardness (Vickers hardness) H of the structural member measured atin-service inspection time. The operation history data includes thestart count n representing the number of times a start has been made;specifically, the total start count N, the cold start count ncrepresenting the number of cold starts, the warm start count nwrepresenting the number of warm starts, and the hot start count nhrepresenting the number of hot starts.

[0111] The storage section 2A is stored with the to-be-assessedcomponent data, the design data, the inspection data, and the operationhistory data input from the data input section 1A.

[0112] The calculation section 8 includes a storage section forpre-storing expressions (7) through (10). In the calculation section,various pieces of data stored in the storage section 2A are put intothose expressions, then calculations are carried out in accordance withthe expressions to obtain a thermal fatigue and damage degree φf(experimental value) and an estimation parameter q for the thermalfatigue and damage degree.

[0113] That is, being subjected to stresses repeatedly as the result ofthe turbine being started and stopped over and over again, a componentsuffers thermal fatigue and damage, which can be estimated in terms ofan elastic strain range Δεe. The elastic strain range Δεe is a functionof the number, M, of repetitions of start and stop until a componentcracks, or raptures and the hardness H of the component and representedby

Δεe=C ₁ M ^(α1) +C ₂ ·M ^(α2)  (7)

[0114] where C1=C₁=10^(β)1·^(H+β)2, α₁=β₃·H+β4, and C2, C₂, α₁, β₁, β₂,β₃, β₄ are constants.

[0115] On the other hand, the elastic strain range Δεe of a region whoselife is assessed is a function of strain concentration coefficient K,stress σ, and elastic coefficient E and represented by

Δεe=2Kε(σ/E)  (8)

[0116] Therefore, measuring the hardness H of an in-service member andknowing the stress σ allow the number M of repetitions of start andstop, until a crack is produced in that member, to be estimated.

[0117] For the start count n, there are three patterns: cold start countnc, warm start count nw, and hot start count nh. Expression (9) thataccumulates the ratio, n/M, of the start count n to the repetition countM for each start pattern is defined to be the thermal fatigue and damagedegree φf.

φf=nc/Mc+nw/Mw+nh/Mh  (9)

[0118] On the other hand, even if the total start count N remainsunchanged, the thermal fatigue and damage degree φf varies due to astress resulting from a temperature difference between start and stoptimes and different start patterns.

[0119] Thus, taking the start patterns, the start count and the stressesinto account, the thermal fatigue and damage degree estimation parameterq is obtained by

q=N(σc·nc/N+σw·nw/N+σh·nh/N)^(α)  (10)

[0120] where α is a constant, σc is the thermal stress at cold starttime, σw is the thermal stress at warm start time, σh is the thermalstress at hot start time, N is the total start count, nc is the coldstart count, nw is the warm start count, and nh is the hot start count.

[0121] The thermal fatigue and damage degree φf and the thermal fatigueand damage degree estimation parameter q thus calculated are output tothe storage section 9. In the storage section 9, therefore, the thermalfatigue and damage degree φf and the thermal fatigue and damage degreeestimation parameter q are stored in combination as data for eachto-be-assessed region or portion of each of many members.

[0122]FIG. 4 shows data plots indicating a relationship between thethermal fatigue and damage degree φf and the damage degree estimationparameter q, in which a linear function expressed by an approximationexpression (11) explained as follows is also denoted. As apparent fromFIG. 4, the data plots can be substantially approximated to the linearfunction.

[0123] In the approximation expression calculation section 10, anapproximation expression for the thermal fatigue and damage degree φf isobtained, that indicates the relationship of the thermal fatigue anddamage degree φf and the thermal fatigue and damage degree estimationparameter q for each to-be-assessed region of each component. Theapproximation expression is calculated from combined data of the thermalfatigue and damage degree φf and the thermal fatigue and damage degreeestimation parameter q stored in the storage section 4 for each regionof each member by expression (11), which represents a constant Cf,estimation parameter q and thermal fatigue and damage degree φf for eachcomponent by a linear approximation expression.

φf=Cf·q  (11)

[0124] In expression (10) α is obtained for each region of eachcomponent, and an appropriate parameter value that most closelyapproaches expression (11) is calculated.

[0125] Next, as shown in FIG. 3B, the probabilistic residual life of thethermal fatigue and damage degree is predicted and analyzed. The systemof FIG. 3B is composed of a Weibull statistical processing calculationsection 11 for predicting and analyzing the probabilistic residual lifeof the thermal fatigue and damage degree on the basis of thecomputational results by the approximation expression calculationsection 10 of FIG. 3A and a thermal fatigue and damage degreeprobabilistic estimation calculation section 12.

[0126] The Weibull statistical processing calculation section 11calculates the Weibull coefficient m and the scale parameter β byWeibull statistical analysis for grasping variations in field dataquantitatively as described in connection with FIG. 1B.

[0127] The thermal fatigue and damage degree probabilistic estimationcalculation section 12 can estimate the thermal fatigue and damagedegree φf probabilistically by substituting the Weibull coefficient mand the scale parameter β obtained by the Weibull statistical processingcalculation section 11 into the expression

φf=Cf·q(β·^(m){square root}{square root over (ln(1−Pf)⁻¹)})  (12)

[0128] where Pf is the cumulative probability (the probability offailure).

[0129]FIGS. 5A to 5C illustrate the function of a system comprising acalculation system that carries out calculations by an estimationexpression for estimating the life of a component probabilistically anda device for assessing its life in accordance with the calculations.

[0130]FIG. 5A and 5C show the calculation apparatus that carries outcalculations by an estimation expression for estimating the life of acomponent probabilistically. The calculation system comprises an optionsection 13 for determining items to be performed, a data input andstorage section 14 for inputting necessary data and storing it, a damagedegree calculation section 15 for calculating the damage degree, astorage section 16 for storing the calculation of the damage degree, aninput section 1B for inputting information about the object ofassessment, a calculation section 17 for calculating approximation andestimation expressions on the basis of data from the storage section 16,and a storage and output section 18 for storing the approximation andestimation expressions.

[0131] The option section 13 can selectively perform the following;

[0132] 1) Calculates the creep damage degree and the thermal fatigue anddamage degree and stores the results in the storage section;

[0133] 2) Obtains the approximation expression for estimating the creepdamage and the expression for estimating probabilistically the creepdamage degree on calculations and obtains the approximation expressionfor estimating the thermal fatigue and damage degree and the expressionfor estimating probabilistically the thermal fatigue and damage degreeon calculations;

[0134] 3) Assesses the life probabilistically.

[0135] A selection can be made among these options through selectbuttons (not shown) by way of example.

[0136] In the input and storage section 14, component data, operationhistory data, inspection data, and design data are input and stored. Thecomponent data includes unit name, member name, region name, etc. Theoperation data includes start/stop count, operation time, etc. Theinspection data includes the hardness of a member, etc. The design dataincludes temperature, stress, etc.

[0137] The damage degree calculation section 15 calculates the creepdamage degree φc based on expression (4) and the thermal fatigue anddamage degree if based on expression (9) and stores the results in thestorage section 16.

[0138] In the input section 1B, data for a member or region for whichapproximation and estimation expressions are to be obtained is enteredand the object of estimation is identified. In the calculation section17, if M or more pieces of data have been obtained as the calculationsof the damage degree of the identified member and region, theapproximation expression for estimating the creep damage and theexpression for estimating probabilistically the creep damage degree arecalculated. Also, in the calculation section 17, the approximationexpression for estimating the thermal fatigue and damage degree and theexpression for estimating probabilistically the thermal fatigue anddamage degree are calculated likewise. In the storage and output section18, these expressions are stored and then output as required.

[0139] Next, a life assessment apparatus will be described withreference to FIG. 5C. The apparatus is composed of an estimation unit,component and region data input section 23, a calculation section 24 forlife assessment based on estimation expressions, and an output section27 for outputting the results of assessment.

[0140] In the data input section 23, data necessary for assessment, suchas assessment unit, member, operation time, start/stop count,temperature, stress, and cumulative probability Pf, are input.

[0141] In the calculation section 24, the creep damage degreeprobabilistic estimation and the thermal fatigue and damageprobabilistic estimation are performed, and in the output section 27 theresults of estimation are output.

[0142]FIG. 6 shows the exemplary results of probabilistic estimation ofthe creep damage degree φc of a turbine member by a steam turbine memberlife assessment device. FIG. 7 shows the exemplary results ofprobabilistic estimation of the thermal fatigue and damage degree φf.FIG. 6 plots the probabilistically estimated creep damage degree φc of amember of a steam turbine against the operation time for cumulativeprobability Pf=0.05, 0.87 and 0.95. In FIG. 7, the probabilisticallyestimated thermal fatigue and damage degree φf of the steam turbinemember is plotted against the start count of the steam turbine unit forcumulative probability Pf=0.05, 0.44 and 0.95.

[0143] The curves of FIGS. 6 and 7 confirm that, if the creep damagedegree φc and the thermal fatigue and damage degree φf are deliveredfrom the hardness which is measured at in-service inspection time andthe cumulative probability Pf=0.87 and 0.44 are determined from theequations (6) and (12), the residual life can probabilistically bepredicted with precision based on the creep damage degree φc and thethermal fatigue and damage degree φf for each component of the steamturbine.

[0144] In this way, according to the equipment of this embodiment, theprocess of consumption of the life can be simulated for any cumulativeprobability Pf.

[0145] The above embodiment of the present invention has been describedin terms of the rotor of a steam turbine as a structural member used ata high in-service temperature. This is not restrictive. The principlesof the present invention can be applied to any other structural memberused at high in-service temperatures.

[0146] Another embodiment of the present invention will be describedwith reference to FIGS. 8 to 13.

[0147]FIG. 8 shows equipment for assessing the life of a member. Thislife assessment equipment comprises an estimation section 51 forestimating probabilistically the hardness of a turbine member subjectedto a high in-service temperature, an assessment or estimation section 52for estimating or assessing the thermal fatigue and damage degree of theturbine member, and an assessment section 53 for assessing the creepdamage degree of the turbine member.

[0148] The estimation section 51 comprises a data input section 61 forinputting data concerning a member, a calculation section 62 forexecuting calculations in accordance with an expression that estimatesthe hardness of the member on the basis of the input data, and an outputsection 63 for outputting the results from the calculation section 62.In the estimation section 51, the hardness of the turbine member at anytime can be estimated on the basis of the Weibull statisticalanalysis-based probabilistic estimation expression as will be describedlater.

[0149] The estimation section 52 comprises a data input section 71 forinputting data concerning a member, a calculation section 72 forcalculating the thermal fatigue and damage degree on the basis of theinput data, and an output section 73 for outputting the results from thecalculation section 72. In the estimation section 52, the thermalfatigue and damage degree is estimated, or evaluated from the estimatedvalue for hardness from the section 51, and the thermal stress, thetemperature and the start count of the turbine member.

[0150] The estimation section 53 comprises a data input section 81 forinputting data concerning a member, a calculation section 82 forcalculating the creep damage degree, and an output section 33 foroutputting the results from the calculation section 82. In theestimation section 53, the creep damage degree is estimated, orevaluated from the estimated value for hardness from the section 51, andthe steady-state stress, the temperature and the operation time of theturbine member on the basis of cumulative damage rules.

[0151] In FIG. 9, the hardness estimation section 51 is illustrated indetail. As shown in FIG. 9, in the turbine member's life assessmentequipment, time-varying hardness data is stored over a long period oftime, say, fifteen years. The hardness of the turbine member isestimated probabilistically by subjecting the hardness data to Weibullstatistical analysis.

[0152] A piece of each member is prepared at manufacture time. Itsinitial hardness at manufacture time and the subsequent hardness areexamined. The hardness H is plotted against the operation time t asshown in FIG. 10. It has been found that the plot of FIG. 10 can beapproximated by a linear function as indicated by expression (33). InFIG. 10, the hardness H is represented in terms of Vickers hardness. Anyother unit instead of the Vickers hardness may represent the hardness.In this case as well, the data plot of FIG. 10 can be made toapproximate to expression (33).

H=at+b  (33)

[0153] Also, it has been found that variations (μ=experimentalvalue/estimated value) in data in the relationship of the operation timeand the hardness can be made to approximate closely to the Weibulldistribution as shown in FIG. 11. The Weibull coefficient and the scaleparameter can therefore be determined from variations in data and thehardness H can be estimated probabilistically by

H=(at+b)(β·^(m){square root}{square root over (ln(1−Pf)⁻¹)})  (34)

[0154] In the data input section 51 shown in FIG. 9, evaluationcomponent data, hardness data and evaluation time data are input. Dataconcerning a component to be evaluated include the name of a unit intowhich the component is incorporated (e.g., a steam turbine unit), thename of a member for identifying the material of the component, and thename of the component. For the hardness data, (i) when initial hardnessis input, the initial hardness H0 is input, (ii) when the hardness atn-service inspection time is input, the operation time t1 throughhardness measurement at in-service inspection time and the hardness H1are input, and (iii) when a cumulative probability Pf is directlyspecified, an appropriate cumulative probability Pf is input. For theevaluation time data, an evaluation time th through the time ofevaluation is input.

[0155] Further, in the calculation section 62 shown in FIG. 9, thehardness at evaluation time is estimated probabilistically by theestimation expression as follows. That is, taking variations in thehardness of a member according to its material characteristics intoaccount, cumulative probabilities Pf corresponding to the initialhardness and the hardness at in-service inspection time are calculatedin the calculation section 121 as follow:

[0156] (i) When the initial hardness is input, the cumulativeprobability Pf0 corresponding to the initial hardness is determined by

Pf0=1−exp{−(μ0/β)^(m)}  (35)

[0157] where H is the member's hardness, t is the member's totaloperation time, a and b are constants, m is the Weibull coefficient, βis the scale parameter, Pf is the cumulative probability correspondingto the initial hardness of the member, and μ0 is initial hardness(experimental value)/hardness (estimated value).

[0158] Here, initial hardness (experimental value)=H0

total operation time: t=t0=0

hardness of the member H=a t0+b=b

[0159] (ii) When the hardness at in-service inspection time is input,the corresponding cumulative probability is determined by

Pf1=1−exp{−(μ1/β)^(m)}  (36)

[0160] where μ1 is hardness at in-service inspection time (experimentalvalue)/hardness (estimated value).

[0161] Here, hardness at in-service inspection time (experimentalvalue)=H1

total operation time: t=t1

hardness of the member H=a t0+b=b

[0162] (iii) When Pf is directly specified, the hardness can beestimated utilizing the specified Pf and the evaluation time t.

[0163] Next, in the hardness calculation section 122, the hardness atevaluation time is calculated using the probabilities Pf0 and Pf1calculated by the calculation section 121 or the directly specified Pfand the total operation time t at evaluation time.

[0164] The hardness as the calculation result at the evaluation time andthe cumulative probability Pf corresponding to the hardness at theevaluation time is output from the output section 63 shown in FIG. 9.

[0165]FIG. 12 shows the details of the turbine member thermal fatigueand damage degree assessment section 52. In the data input section 71,input data include calculation data, component data, design data, andoperation data (operation history data). The calculation data is thehardness of a turbine member (corresponding to the output of the memberhardness estimation section 1). The component data includes the unitname, member name, and region name. The design data includes thetemperature T, the thermal stress σc at cold start time, the thermalstress σw at warm start time, the thermal stress σh at hot start time,and the generic thermal stress σ for these stresses. The operation dataincludes the total start count N, the cold start count nc, the warmstart count nw, and the hot start count nh.

[0166] In the calculation section 72 shown in FIG. 12, the thermalfatigue and damage degree is calculated from the input data from thedata input section 61 and the hardness H at evaluation time estimated bythe hardness estimation section 51.

[0167] The thermal fatigue and damage degree of the member resultingfrom being subjected to repeated stresses due to the start and stop ofthe turbine can estimate the strain range Δεe from a function of thenumber of repetitions N through the generation of a crack and thehardness H as a low-cycle fatigue characteristic by

Δεe=C1M ^(α1) +C2M ^(α2)  (37)

[0168] The strain range of Δεe of a life evaluation region isrepresented as a function of the strain concentration coefficient Kε,the stress σ and the elastic coefficient E as follows:

Δεe=2Kε(σ/E)  (38)

[0169] Therefore, knowing the stress σ allows the number of repetitions(the number of occurrences of rupture) M until cracking occurs in theturbine member to be estimated using the hardness H at evaluation timeobtained by the hardness estimation section 51.

[0170] For the start count n, there are three patterns: cold start countnc, warm start count nw, and hot start count nh. The accumulation of theratio, n/M, of the start count n to the repetition count M through thetime of occurrence of cracking for each start pattern is defined to bethe thermal fatigue and damage degree φf as follows:

φf=nc/Mc+nw/Mw+nh/Mh Here, C ₁=10^(β)1^(H+β)2, α₁=β₃ ·H+β4, and  (39)

[0171] C₂, α₁, β₁, β₂, β₃, β₄ are constants, Δεe is the strain range ofthe life assessment region, K is the strain concentration coefficient, σis the stress, M is the number of repetitions through the time ofoccurrence of cracking, E is the elastic coefficient, nc is the coldstart count, nw is the warm start count, nh is the hot start count, Mcis the number of repetitions through the time of occurrence of crackingat the cold start time, Mw is the number of repetitions through the timeof occurrence of cracking at the cold start time, Mh is the number ofrepetitions through the time of occurrence of cracking at the hot starttime, and φf is the thermal fatigue and damage degree.

[0172]FIG. 13 shows the details of the turbine member creep rupture anddamage degree assessment section 53. In the data input section 81, inputdata include calculation data, component data, design data, andoperation data (operation history data). The calculation data is thehardness of a turbine member (corresponding to the output of the memberhardness estimation section 51). The component data includes the unitname, member name, and region name. The design data includes thetemperature T of the turbine member in the steady state, thesteady-state stress σ. The operation data includes the total operationtime t.

[0173] In the estimation section 82 shown in FIG. 13, the creep damagedegree is calculated from the input data from the data input section 81and the hardness H at evaluation time from the hardness estimationsection 51. Specifically, the creep damage degree is estimated(calculated) based on expressions (40) through (43).

[0174] The creep damage degree due to steady-state operation underconditions of a high in-service temperature and a constant stress allowsthe LarsonMiller parameter P to be estimated from the hardness H and thesteady-state stress (load stress) by

P′=A1(σ)H+B1(σ)  (40)

[0175] On the other hand, the Larson-Miller parameter p is represented,as a function of the in-service temperature T(° C.) and the creeprupture life tr, by

tr=10^({p′/(T+273)−C})  (41)

[0176] where C is the material constant, T is the in-servicetemperature, and tr is creep rupture life,

φc=t/(tr+t) or φc=t/tr  (42)

[0177] where φc is the creep damage degree, and

[0178] where, when data of the hardness of the portion under a highin-service temperature and a high stress of the member whose life is tobe assessed is used, φc=t/(tr+t) is employed, and when data of thehardness of the portion under a high in-service temperature and a lowstress is used to assess the portion of the member under a highin-service temperature and a high stress, φc=t/tr is employed.

[0179] The estimation result of the creep damage degree is output fromthe output section 83 of FIG. 13.

[0180] In the calculation section 121 of FIG. 9, the cumulativeprobability Pf obtained from the hardness of a member at any point oftime can be estimated on the basis of the probabilistic estimationexpression based on the Weibull statistical analysis; this cumulativeprobability Pf may be input, as inspection data, to the input section 23shown in FIG. 5C to estimate the creep damage degree in the system ofFIGS. 5A to 5C.

[0181] Furthermore, in the calculation section 121, the cumulativeprobability Pf can be estimated. This cumulative probability Pf may beused to estimate the creep damage degree. That is, the cumulativeprobability Pf may be so inputted to the input section 23 shown in FIG.5C as to estimate the creep damage degree. The hardness H obtained fromthe cumulative probability Pf may be also so input to the input section1A shown in FIG. 1A to estimate the thermal fatigue and damage degree.That is, the cumulative probability may be utilized to estimate thethermal fatigue and damage degree.

[0182] As apparent from the description, the above described method andsystem are realized by a computer system comprising CPU, ROM, RAM andI/F and a computer program for the computer system is so designed as toperform the above described method.

[0183]FIG. 14 illustrates a method of assessing the life of a turbinemember over a network, for example, an internet 95. With the system ofFIG. 14, a server 96 can provide a service over the internet 95 to aclient who desires to assess the life of a member consisting of lowalloy steel. That is, in the system that assesses the life of a member,a terminal 94 on the client side includes an input section 91 and anoutput section 92 and the service providing server 96 includes anestimation section that estimates the creep damage degree and thethermal fatigue and damage degree which have already been described. Theexternal input section 91 is allowed to, as instructed by the server,enter the unit name, the component name, the hardness, the operationtime at the time of hardness measurement or the cumulative probabilityPf, and the operation time and the start/stop count through the time ofevaluation. The estimation section receives those input data over theinternet 95 and then estimates the creep damage degree and the thermalfatigue and damage degree. The output section 92 on the client sidereceives the results of estimation over the internet 95 from theestimation and outputs them.

[0184] The external input section 91 is simply a device that inputscommands and data to a computer such as a personal computer, forinstance, a keyboard, a mouse, a tablet, a joystick, a scanner, an OCR,a character recognition system, a voice input system, a video system, abar-code reader, or a microphone. The output section 92 may be anydevice capable of outputting computer-processed information, such as aprinter, a visual display unit, a voice output system, etc.

[0185] The service providing server 96 consists of an informationprocessing terminal, such as a computer, and has server functions forthe internet 95. The internet may be either wired or wireless providedthat it can make digital communications. The internet may contain publiclines.

[0186] In the internet system as shown in FIG. 14, following methods canbe realized. That is, the system can perform a method of assessing thelife of a member subjected to a high in-service temperature for a longperiod comprising the steps of:

[0187] determining a Larson-Miller parameter for the member whose lifeis to be assessed from the in-service temperature and time of the memberand using data established by calculating the creep damage degree on thebasis of cumulative damage rules from the hardness and stress of themember to approximate the relationship between the Larson-Millerparameter and the creep damage degree by an expression including anexponential function;

[0188] prompting a terminal connected through a network to input thein-service time period, of the member whose life is to be assessed;

[0189] assessing the life of the member from the in-service time period,of the member whose life is to be assessed by using the approximateexpression; and

[0190] outputting the assessed life to the terminal.

[0191] The system can also perform a method of assessing the life of amember subjected to a high in-service temperature for a long periodcomprising the steps of:

[0192] determining a Larson-Miller parameter for the member whose lifeis to be assessed from the in-service temperature and service timeperiod during which the member is used in-service temperature and usingdata established by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member toapproximate the relationship between the Larson-Miller parameter and thecreep damage degree by an expression including an exponential functionand further to prepare an expression estimating the creep damage degreeadded with probabilistic statistical processing;

[0193] prompting a terminal connected through a network to input thein-service time period, and the hardness of the member whose life is tobe assessed;

[0194] assessing the life of the member from the in-service time period,of the input member; and

[0195] outputting the assessed life to the terminal.

[0196] Furthermore, the system can perform a method of assessing thelife of a member subjected to a high in-service temperature for a longperiod comprising the steps of:

[0197] inputting a service time period during which the member is usedin-service temperature, whose life is to be assessed from a terminalconnected to a network; and

[0198] according to the input, in a service supplying equipmentconnected to the network, determining a Larson-Miller parameter for themember whose life is to be assessed from the in-service temperature andservice time period during which the member is used in-servicetemperature, assessing the life of the member by the approximateexpression including an exponential function of the relationship betweenthe Larson-Miller parameter and the creep damage degree using dataestablished by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member, andoutputting the assessed life to the terminal.

[0199] Furthermore, the system can also perform a method of assessingthe life of a member subjected to a high in-service temperature for along period comprising the steps of:

[0200] inputting a service time period during which the member is usedin-service temperature and the hardness of the member whose life is tobe assessed from a terminal connected to a network; and

[0201] according to the input, in a service supplying equipmentconnected to the network, determining a Larson-Miller parameter for themember whose life is to be assessed from the in-service temperature andtime of the member, using data established by calculating the creepdamage degree on the basis of cumulative damage rules from the hardnessand stress of the member to approximate the relationship between theLarson-Miller parameter and the creep damage degree by an expressionincluding an exponential function and to assess the life of the memberby an expression estimating the creep damage degree added withprobabilistic statistical processing, and outputting the assessed lifeto the terminal.

[0202] The system can also perform an another method of assessing thelife of a member provided in an apparatus which is started and stoppedover and over again and subjected to a high in-service temperature for along period while the apparatus is being operated comprising the stepsof:

[0203] from an estimation parameter which is a function of a set of thestart count and stress, and data established by calculating thermalfatigue and damage degree based on cumulative damage rules for themember whose life is to be assessed, preparing an approximate expressionof the relationship between the estimation parameter and the thermalfatigue and damage degree;

[0204] prompting a terminal connected through a network to input thestart count of the member whose life is to be assessed;

[0205] assessing the life of the member from the input start count byusing the approximate expression; and

[0206] outputting the assessed life to the terminal.

[0207] The system can also perform a yet another method of assessing thelife of a member provided in an apparatus which is started and stoppedover and over again and subjected to a high in-service temperature for along period while the apparatus is being operated comprising the stepsof:

[0208] using an estimation parameter which is a function of the startcount and thermal stress, and data established by calculating thermalfatigue and damage degree based on cumulative damage rules for themember whose life is to be assessed and approximating the relationshipbetween the estimation parameter and the thermal fatigue and damagedegree and preparing an expression estimating the thermal fatigue anddamage degree added with probabilistic statistical processing;

[0209] prompting a terminal connected through a network to input thestart count and the hardness of the member whose life is to be assessed;

[0210] assessing the life of the member from the input start count andhardness by using the approximate expression; and

[0211] outputting the assessed life to the terminal.

[0212] Furthermore, the system can also perform an another method ofassessing the life of a member provided in an apparatus which is startedand stopped over and over again and subjected to a high in-servicetemperature for a long period while the apparatus is being operatedcomprising the steps of:

[0213] inputting the start count of the member whose life is to beassessed from a terminal connected to a network; and

[0214] according to the input, in a service supplying equipmentconnected to the network, assessing the life of the member by anapproximate expression of the relationship between the estimationparameter and the thermal fatigue and damage degree, which isapproximated from an estimation parameter which is a function of thestart count and thermal stress, and data established by calculatingthermal fatigue and damage degree based on cumulative damage rules forthe member whose life is to be assessed, and outputting the assessedlife to the terminal.

[0215] The system can also perform a further method of assessing thelife of a member provided in an apparatus which is started and stoppedover and over again and subjected to a high in-service temperature for along period while the apparatus is being operated comprising the stepsof:

[0216] inputting the start count and hardness of the member whose lifeis to be assessed from a terminal connected to a network; and

[0217] according to the input, in a service supplying equipmentconnected to the network, using an estimation parameter which is afunction of the start count and thermal stress, and data established bycalculating thermal fatigue and damage degree based on cumulative damagerules, for the member whose life is to be assessed, approximating therelationship between the estimation parameter and the thermal fatigueand damage degree, assessing the life of the member by an expressionestimating the thermal fatigue and damage degree added withprobabilistic statistical processing, and outputting the assessed lifeto the terminal.

[0218] As described thus far, the present invention provides thefollowing advantages:

[0219] (1) Conventionally, in assessing the life of a turbine member,its hardness is measured at in-service inspection time and used toassess the member's life. However, precise life assessment cannot bemade without hardness measurement at in-service inspection time,resulting in failure to make quick life assessment. By contrast, theinventive life assessment method and equipment collect variations inhardness of the member with time and probabilistically estimates thehardness of the turbine member. If the initial hardness (hardness atmanufacture time) or the hardness at in-service inspection time isavailable, then the hardness at the time of evaluation can be estimatedbased on that hardness and a cumulative probability Pf corresponding tothe hardness can be determined.

[0220] (2) In the absence of hardness data, on the other hand, thehardness at evaluation time can be estimated by estimating thecumulative probability Pf. Even in the case where hardness data isknown, the hardness corresponding to the cumulative probability Pf canbe estimated by specifying Pf.

[0221] (3) Moreover, the thermal fatigue material characteristic and thecreep material characteristic is determined as a function of hardness.The use of estimated hardness at evaluation time allows life assessmentto be made precisely and quickly.

[0222] (4) According to the present invention, the life assessment canbe speeded up and the life assessment cost can be reduced in any distantlocation by receiving input information over the internet 95 from aclient, assessing the life of a component through the use of theinventive assessment server, and sending the results of assessment tothe client.

[0223] According to the present invention, as described above, a lifeassessment method and equipment can be provided which permit the life ofa turbine member subjected to a high in-service temperature to beassessed by collecting the time-varying hardness of the member andestimating probabilistically the hardness of the turbine member.

[0224] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A method of assessing the life of a membersubjected to a high in-service temperature for a long period comprisingthe steps of: determining a Larson-Miller parameter for the member whoselife is to be assessed from the in-service temperature and a servicetime period during which the member is used in-service temperature, andcalculating the creep damage degree on the basis of cumulative damagerules from the hardness and stress of the member to establish data; andapproximating the relationship between the Larson-Miller parameter andthe creep damage degree by an expression including an exponentialfunction.
 2. The method according to claim 1, further comprising thestep of assessing the life of the member from the in-service temperatureand in-service time period, period of the member whose life is to beassessed using the approximate expression.
 3. The method according toclaim 1, wherein the Larson-Miller parameter P is calculated by anexpression given as P=(T+273)(log t+C)where C is the material constant,T is the in-service temperature and t is the in-service time period,period, and the creep damage degree φc based upon the cumulative damagerules is calculated by an expression given as P′=A(σ)H+B(σ) where σ isthe stress, and H is the hardness, P′=(T+273)(log tr+C) where C is thematerial constant, T is the in-service temperature, and tr is creeprupture life, φc=t/(tr+t) or φc=t/tr where φc is the creep damagedegree, and where, when data of the hardness of the portion under a highin-service temperature and a high stress of the member whose life is tobe assessed is used, φc=t/(tr+t) is employed, and when data of thehardness of the portion under a high in-service temperature and a lowstress is used to assess the portion of the member under a highin-service temperature and a high stress, φc=t/tr is employed.
 4. Themethod according to claim 3, wherein the relationship between theLarson-Miller parameter and the creep damage degree uses an approximateexpression including an exponential function given as φc=1−exp(A·P ^(B))where A and B are constants.
 5. A method of assessing the life of amember subjected to a high in-service temperature for a long periodcomprising the steps of: determining a Larson-Miller parameter for themember whose life is to be assessed from the in-service temperature andservice time period during which the member is used in-servicetemperature and using data established by calculating the creep damagedegree on the basis of cumulative damage rules from the hardness andstress of the member to approximate the relationship between theLarson-Miller parameter and the creep damage degree by an expressionincluding an exponential function; and estimating the creep damagedegree by adding probabilistic statistical processing to the approximateexpression.
 6. The method according to claim 5, wherein theLarson-Miller parameter P is calculated by an expression given asP=(T+273)(log t+C)where C is the material constant, T is a service timeperiod during which the member is used in-service temperature and t isthe in-service time period, and the creep damage degree φc based uponthe cumulative damage rules is calculated by an expression given asP′=A1(σ)H+B1(σ) where σ is the stress, and H is the hardness,P′=(T+273)(log tr+C) where C is the material constant, T is thein-service temperature, and tr is the creep rupture life, φc=t/(tr+t) orφc=t/tr where φc is the creep damage degree, and where, when data of thehardness of the portion under a high in-service temperature and a highstress of the member whose life is to be assessed is used, φc=t/(tr+t)is employed, and when data of the hardness of the portion under a highin-service temperature and a low stress is used to assess the portion ofthe member under a high in-service temperature and a high stress,φc=t/tr is employed.
 7. The method according to claim 6, wherein therelationship between the Larson-Miller parameter and the creep damagedegree uses an approximate expression including an exponential functiongiven as φc=1−exp(A·P ^(B)) where A and B are constants.
 8. The methodaccording to claim 7, wherein the creep damage degree where theprobabilistic statistical processing is added to the approximateexpression is estimated by an expression given as φc={1−exp(A·P^(B))}·{β·^(m){square root}{square root over (ln(1−Pf)⁻¹)}} where m isthe Weibull coefficient, β is the scale parameter, and Pf is thecumulative probability.
 9. The method according to claim 5, furthercomprising the step of assessing the life of the member by inputting acumulative probability into the expression added with the probabilisticstatistical processing.
 10. The method according to claim 9, wherein thecumulative probability is estimated from the hardness of the member. 11.The method according to claim 10, wherein the cumulative probability Pfcorresponds to the cumulative probability Pf defined by the followingexpression and the cumulative probability Pf depending on the hardnessis obtained by an expression given as Pf=1−exp{−(μ/β)^(m)}where m is theWeibull coefficient, β is the scale parameter, and μ is the hardness ofthe member (experimental value)/the hardness of the member (estimatedvalue), and further the estimated value of the hardness of the member isobtained by an equation using the least squares method given as at+b,where t is the total operation time when the hardness of the member ismeasured, and a and b are constants.
 12. The method according to claim9, wherein the step of assessing the life provides the graph regardingthe operation time of the member and the creep damage degree and theremaining life of the member.
 13. A method of assessing the life of amember subjected to a high in-service temperature for a long period,wherein the hardness of the member is estimated by an expression givenas H=(at+b)(β^(m){square root}{square root over (ln(1−Pf)⁻¹)})wherein His the hardness of the member, t is the total operation time when thehardness of the member is measured, a and b are constants, m is theWeibull coefficient, β is the scale parameter, and Pf is the cumulativeprobability corresponding to the hardness of the member.
 14. A method ofassessing the life of a member provided in an apparatus which is startedand stopped over and over again and subjected to a high in-servicetemperature for a long period while the apparatus is being operatedcomprising the steps of: calculating an estimation parameter which is afunction of a set of the start count and thermal stress, and thermalfatigue and damage degree based on cumulative damage rules for themember whose life is to be assessed and establishing data; andapproximating the relationship between the estimation parameter and thethermal fatigue and damage degree by an approximate expression.
 15. Themethod according to claim 14, where the estimation parameter is anexponential function, and the approximate expression showing therelationship between the estimation parameter and the thermal fatigueand damage degree is a linear equation.
 16. The method according toclaim 15, wherein the estimation parameter q is given by an expressionof q=N(σc·nc/N+σw·nw/N+σh·nh/N)^(α) where α is the constant, σc is thethermal stress of the member at cold start time, σw is the thermalstress of the member at warm start time, σh is the thermal stress of themember at hot start time, N is the total start count, no is the coldstart count, nw is the warm start count, and nh is the hot start count,and the thermal fatigue and damage degree is approximated by anexpression given as φf=Cf·q where Cf is a constant.
 17. The methodaccording to claim 14, further comprising the step of using theapproximate expression to assess the life of the member whose life is tobe assessed from the start count of the member.
 18. A method ofassessing the life of a member provided in an apparatus which is startedand stopped over and over again and subjected to a high in-servicetemperature for a long period while the apparatus is being operatedcomprising the steps of: using an estimation parameter which is afunction of the start count and thermal stress, and data established bycalculating thermal fatigue and damage degree based on cumulative damagerules, for the member whose life is to be assessed, and approximatingthe relationship between the estimation parameter and the thermalfatigue and damage degree by an approximate expression; and estimatingthe thermal fatigue and damage degree by adding probabilisticstatistical processing to this approximate expression.
 19. The methodaccording to claim 18, where the estimation parameter is an exponentialfunction, and the approximate expression showing the relationshipbetween the estimation parameter and the thermal fatigue and damagedegree is a linear equation.
 20. The method according to claim 19,wherein the estimation parameter q is given by an expression ofq=N(σc·nc/N+σw·nw/N+σh·nh/N)^(α) where α is the constant, σc is thethermal stress of the member at cold start time, σw is the thermalstress of the member at warm start time, σh is the thermal stress of themember at hot start time, N is the total start count, nc is the coldstart count, nw is the warm start count, and nh is the hot start count,and the thermal fatigue and damage degree is approximated by anexpression given as φf=C·q where Cf is a constant.
 21. The methodaccording to claim 20, wherein the thermal fatigue and damage degreeobtained by adding the probabilistic statistical processing to theapproximate expression is given by an expression ofφf=Cf·q(β·^(m){square root}{square root over (ln(1−Pf)⁻¹)})where m isthe Weibull coefficient, β is the scale parameter, and Pf is thecumulative probability.
 22. The method according to claim 18, furthercomprising the step of assessing the life of the member by inputting acumulative probability into the expression added with the probabilisticstatistical processing.
 23. The method according to claim 22, whereinthe cumulative probability is estimated by the hardness of the member.24. The method according to claim 23, wherein the cumulative probabilityPf corresponds to the cumulative probability Pf defined by the followingexpression, the cumulative probability Pf depending on the hardness isobtained by an expression given as Pf=1−exp{−(μ/β)^(m)}where m is theWeibull coefficient, β is the scale parameter, and μ is the hardness ofthe member (experimental value)/the hardness of the member (estimatedvalue), and further the estimated value of the hardness of the member isobtained by an expression using the least squares method given as at+bwhere t is the total operation time when the hardness of the member ismeasured, and a and b are constants.
 25. The method according to claim22, wherein the step of assessing the life provides a graph showingrelationship between the start count, and the thermal fatigue and damagedegree of the member, and the remaining life of the member.
 26. Anapparatus for assessing the life of a member subjected to a highin-service temperature for a long period, comprising: means fordetermining a Larson-Miller parameter for the member whose life is to beassessed from the in-service temperature and a service time periodduring which the member is used in-service temperature, and calculatingthe creep damage degree on the basis of cumulative rules from thehardness and stress of the member to establish data; and means forapproximating the relationship between the Larson-Miller parameter andthe creep damage degree by an expression including an exponentialfunction.
 27. The apparatus according to claim 26, further comprisingmeans for assessing the life of the member from the in-servicetemperature and in-service time period, period of the member whose lifeis to be assessed using the approximate expression.
 28. The apparatusaccording to claim 26, wherein the Larson-Miller parameter P iscalculated by an expression given as P=(T+273)(log t+C)where C is thematerial constant, T is the in-service temperature and t is thein-service time period, period, and the creep damage degree φc basedupon the cumulative damage rules is calculated by an expression given asP′=A(σ)H+B(σ) where σ is the stress, and H is the hardness,P′(T+273)(log tr+C) where C is the material constant, T is thein-service temperature, and tr is creep rupture life, φc=t/(tr+t) orφc=t/tr where φc is the creep damage degree, and where, when data of thehardness of the portion under a high in-service temperature and a highstress of the member whose life is to be assessed is used, φc=t/(tr+t)is employed, and when data of the hardness of the portion under a highin-service temperature and a low stress is used to assess the portion ofthe member under a high in-service temperature and a high stress,φc=t/tr is employed.
 29. The apparatus according to claim 28, whereinthe relationship between the Larson-Miller parameter and the creepdamage degree uses an approximate expression including an exponentialfunction given as φc=1−exp(A·P ^(B))where A and B are constants.
 30. Anapparatus for assessing the life of a member subjected to a highin-service temperature for a long period comprising: means fordetermining a Larson-Miller parameter for the member whose life is to beassessed from the in-service temperature and service time period duringwhich the member is used in-service temperature and using dataestablished by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member toapproximate the relationship between the Larson-Miller parameter and thecreep damage degree by an expression including an exponential function;and means for estimating the creep damage degree by adding probabilisticstatistical processing to the approximate expression.
 31. The apparatusaccording to claim 30, wherein the Larson-Miller parameter P iscalculated by an expression given as P=(T+273)(log t+C) where C is thematerial constant, T is a service time period during which the member isused in-service temperature and t is the in-service time period, and thecreep damage degree φc based upon the cumulative damage rules iscalculated by an expression given as P′=A1(σ)H+B1(σ)Where σ is thestress, and H is the hardness, P′=(T+273)(log tr+C) where T is thein-service temperature, and tr is the creep rupture life, φc=t/(tr+t) orφc=t/tr where φc is the creep damage degree, and where, when data of thehardness of the portion under a high in-service temperature and a highstress of the member whose life is to be assessed is used, φc=t/(tr+t)is employed, and when data of the hardness of the portion under a highin-service temperature and a low stress is used to assess the portion ofthe member under a high in-service temperature and a high stress,φc−t/tr is employed.
 32. The apparatus according to claim 31, whereinthe relationship between the Larson-Miller parameter and the creepdamage degree uses an approximate expression including an exponentialfunction given as φc=1−exp(A·P ^(B))where A and B are constants.
 33. Theapparatus according to claim 32, wherein the creep damage degree wherethe probabilistic statistical processing is added to the approximateexpression is estimated by an expression given as φc={1−exp(A·P^(B))}·{β·^(m){square root}{square root over (ln(1−Pf)⁻¹)}}where m isthe Weibull coefficient, β is the scale parameter, and Pf is thecumulative probability.
 34. The apparatus according to claim 30, furthercomprising the step of assessing the life of the member by inputting acumulative probability into the expression added with the probabilisticstatistical processing.
 35. The apparatus according to claim 34, whereinthe cumulative probability is estimated from the hardness of the member.36. The apparatus according to claim 35, wherein the cumulativeprobability Pf corresponds to the cumulative probability Pf defined bythe following expression and the cumulative probability Pf depending onthe hardness is obtained by an expression given asPf=1−exp{−(μ/β)^(m)}where m is the Weibull coefficient, β is the scaleparameter, and μ is the hardness of the member (experimental value)/thehardness of the member (estimated value), and further the estimatedvalue of the hardness of the member is obtained by an equation using theleast square method given as at+b, where t is the total operation timewhen the hardness of the member is measured, and a and b are constants.37. The apparatus according to claim 30, wherein said assessing meansprovides the graph regarding the operation time of the member and thecreep damage degree and the remaining life of the member.
 38. Anapparatus for assessing the life of a member subjected to a highin-service temperature for a long period, wherein the hardness of themember is estimated by an expression given as H=(at+b)(β·^(m){squareroot}{square root over (ln(1−Pf)⁻¹)})wherein H is the hardness of themember, t is the total operation time when the hardness of the member ismeasured, a and b are constants, m is the Weibull coefficient, β is thescale parameter, and Pf is the cumulative probability corresponding tothe hardness of the member.
 39. An apparatus for assessing the life of amember provided in an apparatus which is started and stopped over andover again and subjected to a high in-service temperature for a longperiod while the apparatus is being operated comprising: means forcalculating an estimation parameter which is a function of a set of thestart count and thermal stress, and thermal fatigue and damage degreebased on cumulative damage rules for the member whose life is to beassessed and establishing data; and means for approximating therelationship between the estimation parameter and the thermal fatigueand damage degree by an approximate expression.
 40. The apparatusaccording to claim 39, where the estimation parameter is an exponentialfunction, and the approximate expression showing the relationshipbetween the estimation parameter and the thermal fatigue and damagedegree is a linear equation.
 41. The apparatus according to claim 40,wherein the estimation parameter q is given by an expression ofq=N(σc·nc/N+σw·nw/N+σh·nh/N)^(α) where α is the constant, σc is thethermal stress of the member at cold start time, σw is the thermalstress of the member at warm start time, σh is the thermal stress of themember at hot start time, N is the total start count, nc is the coldstart count, nw is the warm start count, and nh is the hot start count,and the thermal fatigue and damage degree is approximated by anexpression given as φf=Cf·q where Cf is a constant.
 42. The apparatusaccording to claim 41, further comprising means for using theapproximate expression to assess the life of the member whose life is tobe assessed from the start count of the member.
 43. An apparatus forassessing the life of a member provided in an apparatus which is startedand stopped over and over again and subjected to a high in-servicetemperature for a long period while the apparatus is being operatedcomprising: means for using an estimation parameter which is a functionof the start count and thermal stress, and data established bycalculating thermal fatigue and damage degree based on cumulative damagerules, for the member whose life is to be assessed, and approximatingthe relationship between the estimation parameter and the thermalfatigue and damage degree by an approximate expression; and means forestimating the thermal fatigue and damage degree by adding probabilisticstatistical processing to this approximate expression.
 44. The apparatusaccording to claim 43, where the estimation parameter is an exponentialfunction, and the approximate expression showing the relationshipbetween the estimation parameter and the thermal fatigue and damagedegree is a linear equation.
 45. The apparatus according to claim 44,wherein the estimation parameter q is given by an expression ofq=N(σc·nc/N+σw·nw/N+σh·nh/N)^(α) where α is the constant, σc is thethermal stress of the member at cold start time, σw is the thermalstress of the member at warm start time, σh is the thermal stress of themember at hot start time, N is the total start count, nc is the coldstart count, nw is the warm start count, and nh is the hot start count,and the thermal fatigue and damage degree is approximated by anexpression given as φf=Cf·q where Cf is a constant.
 46. The apparatusaccording to claim 45, wherein the thermal fatigue and damage degreeobtained by adding the probabilistic statistical processing to theapproximate expression is given by an expression ofφf=Cf·q(β·^(m){square root}{square root over (ln(1−Pf)⁻¹)})where m isthe Weibull coefficient, β is the scale parameter, and Pf is thecumulative probability.
 47. The method according to claim 43, furthercomprising the step of assessing the life of the member by inputting acumulative probability into the expression added with the probabilisticstatistical processing.
 48. The apparatus according to claim 47, whereinthe cumulative probability is estimated by the hardness of the member.49. The apparatus according to claim 48, wherein the cumulativeprobability Pf corresponds to the cumulative probability Pf defined bythe following expression, the cumulative probability Pf depending on thehardness is obtained by an expression given as Pf=1−exp{−(μ/β)^(m)}wherem is the Weibull coefficient, β is the scale parameter, and μ is thehardness of the member (experimental value)/the hardness of the member(estimated value), and further the estimated value of the hardness ofthe member is obtained by an expression using the least square methodgiven as at+b where t is the total operation time when the hardness ofthe member is measured, and a and b are constants.
 50. The apparatusaccording to claim 47, wherein the step of assessing the life provides agraph showing relationship between the start count, and the thermalfatigue and damage degree of the member, and the remaining life of themember.
 51. A method of assessing the life of a member subjected to ahigh in-service temperature for a long period comprising the steps of:determining a Larson-Miller parameter for the member whose life is to beassessed from the in-service temperature and time of the member andusing data established by calculating the creep damage degree on thebasis of cumulative damage rules from the hardness and stress of themember to approximate the relationship between the Larson-Millerparameter and the creep damage degree by an expression including anexponential function; prompting a terminal connected through a networkto input the in-service time period, of the member whose life is to beassessed; assessing the life of the member from the in-service timeperiod, of the member whose life is to be assessed by using theapproximate expression; and outputting the assessed life to theterminal.
 52. A method of assessing the life of a member subjected to ahigh in-service temperature for a long period comprising the steps of:determining a Larson-Miller parameter for the member whose life is to beassessed from the in-service temperature and service time period duringwhich the member is used in-service temperature and using dataestablished by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member toapproximate the relationship between the Larson-Miller parameter and thecreep damage degree by an expression including an exponential functionand further to prepare an expression estimating the creep damage degreeadded with probabilistic statistical processing; prompting a terminalconnected through a network to input the in-service time period, and thehardness of the member whose life is to be assessed; assessing the lifeof the member from the in-service time period and the hardness, of theinput member; and outputting the assessed life to the terminal.
 53. Amethod of assessing the life of a member subjected to a high in-servicetemperature for a long period comprising the steps of: inputting aservice time period during which the member is used in-servicetemperature, whose life is to be assessed from a terminal connected to anetwork; and according to the input, in a service supplying equipmentconnected to the network, determining a Larson-Miller parameter for themember whose life is to be assessed from the in-service temperature andservice time period during which the member is used in-servicetemperature, assessing the life of the member by the approximateexpression including an exponential function of the relationship betweenthe Larson-Miller parameter and the creep damage degree using dataestablished by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member, andoutputting the assessed life to the terminal.
 54. A method of assessingthe life of a member subjected to a high in-service temperature for along period comprising the steps of: inputting a service time periodduring which the member is used in-service temperature and the hardnessof the member whose life is to be assessed from a terminal connected toa network; and according to the input, in a service supplying equipmentconnected to the network, determining a Larson-Miller parameter for themember whose life is to be assessed from the in-service temperature andtime of the member, using data established by calculating the creepdamage degree on the basis of cumulative damage rules from the hardnessand stress of the member to approximate the relationship between theLarson-Miller parameter and the creep damage degree by an expressionincluding an exponential function and to assess the life of the memberby an expression estimating the creep damage degree added withprobabilistic statistical processing, and outputting the assessed lifeto the terminal.
 55. A method of assessing the life of a member providedin an apparatus which is started and stopped over and over again andsubjected to a high in-service temperature for a long period while theapparatus is being operated comprising the steps of: from an estimationparameter which is a function of a set of the start count and thermalstress, and data established by calculating thermal fatigue and damagedegree based on cumulative damage rules for the member whose life is tobe assessed, preparing an approximate expression of the relationshipbetween the estimation parameter and the thermal fatigue and damagedegree; prompting a terminal connected through a network to input thestart count of the member whose life is to be assessed; assessing thelife of the member from the input start count by using the approximateexpression; and outputting the assessed life to the terminal.
 56. Amethod of assessing the life of a member provided in an apparatus whichis started and stopped over and over again and subjected to a highin-service temperature for a long period while the apparatus is beingoperated comprising the steps of: using an estimation parameter which isa function of the start count and thermal stress, and data establishedby calculating thermal fatigue and damage degree based on cumulativedamage rules for the member whose life is to be assessed andapproximating the relationship between the estimation parameter and thethermal fatigue and damage degree and preparing an expression estimatingthe thermal fatigue and damage degree added with probabilisticstatistical processing; prompting a terminal connected through a networkto input the start count and the hardness of the member whose life is tobe assessed; assessing the life of the member from the input start countand hardness by using the approximate expression; and outputting theassessed life to the terminal.
 57. A method of assessing the life of amember provided in an apparatus which is started and stopped over andover again and subjected to a high in-service temperature for a longperiod while the apparatus is being operated comprising the steps of:inputting the start count of the member whose life is to be assessedfrom a terminal connected to a network; and according to the input, in aservice supplying equipment connected to the network, assessing the lifeof the member by an approximate expression of the relationship betweenthe estimation parameter and the thermal fatigue and damage degree,which is approximated from an estimation parameter which is a functionof the start count and thermal stress, and data established bycalculating thermal fatigue and damage degree based on cumulative damagerules for the member whose life is to be assessed, and outputting theassessed life to the terminal.
 58. A method of assessing the life of amember provided in an apparatus which is started and stopped over andover again and subjected to a high in-service temperature for a longperiod while the apparatus is being operated comprising the steps of:inputting the start count and hardness of the member whose life is to beassessed from a terminal connected to a network; and according to theinput, in a service supplying equipment connected to the network, usingan estimation parameter which is a function of the start count andthermal stress, and data established by calculating thermal fatigue anddamage degree based on cumulative damage rules, for the member whoselife is to be assessed, approximating the relationship between theestimation parameter and the thermal fatigue and damage degree,assessing the life of the member by an expression estimating the thermalfatigue and damage degree added with probabilistic statisticalprocessing, and outputting the assessed life to the terminal.
 59. Anapparatus for assessing the life of a member subjected to a highin-service temperature for a long period comprising: means fordetermining a Larson-Miller parameter for the member whose life is to beassessed from the in-service temperature and time of the member andusing data established by calculating the creep damage degree on thebasis of cumulative damage rules from the hardness and stress of themember to approximate the relationship between the Larson-Millerparameter and the creep damage degree by an expression including anexponential function; means for prompting a terminal connected through anetwork to input the in-service time period, of the member whose life isto be assessed; means for assessing the life of the member from thein-service time period, of the member whose life is to be assessed byusing the approximate expression; and means for outputting the assessedlife to the terminal.
 60. An apparatus for assessing the life of amember subjected to a high in-service temperature for a long periodcomprising: means for determining a Larson-Miller parameter for themember whose life is to be assessed from the in-service temperature andservice time period during which the member is used in-servicetemperature and using data established by calculating the creep damagedegree on the basis of cumulative damage rules from the hardness andstress of the member to approximate the relationship between theLarson-Miller parameter and the creep damage degree by an expressionincluding an exponential function and further to prepare an expressionestimating the creep damage degree added with probabilistic statisticalprocessing; means for prompting a terminal connected through a networkto input the in-service time period, and the hardness of the memberwhose life is to be assessed; means for assessing the life of the memberfrom the in-service time period, of the input member; and means foroutputting the assessed life to the terminal.
 61. An apparatus forassessing the life of a member subjected to a high in-servicetemperature for a long period, comprising: means for inputting a servicetime period during which the member is used in-service temperature,whose life is to be assessed from a terminal connected to a network; andmeans for according to the input, in a service supplying equipmentconnected to the network, determining a Larson-Miller parameter for themember whose life is to be assessed from the in-service temperature andservice time period during which the member is used in-servicetemperature, assessing the life of the member by the approximateexpression including an exponential function of the relationship betweenthe Larson-Miller parameter and the creep damage degree using dataestablished by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member, andoutputting the assessed life to the terminal.
 62. An apparatus forassessing the life of a member subjected to a high in-servicetemperature for a long period, comprising: means for inputting a servicetime period during which the member is used in-service temperature andthe hardness of the member whose life is to be assessed from a terminalconnected to a network; and means for according to the input, in aservice supplying equipment connected to the network, determining aLarson-Miller parameter for the member whose life is to be assessed fromthe in-service temperature and time of the member, using dataestablished by calculating the creep damage degree on the basis ofcumulative damage rules from the hardness and stress of the member toapproximate the relationship between the Larson-Miller parameter and thecreep damage degree by an expression including an exponential functionand to assess the life of the member by an expression estimating thecreep damage degree added with probabilistic statistical processing, andoutputting the assessed life to the terminal.
 63. An apparatus forassessing the life of a member provided in an apparatus which is startedand stopped over and over again and subjected to a high in-servicetemperature for a long period while the apparatus is being operatedcomprising: means, from an estimation parameter which is a function of aset of the start count and thermal stress, and data established bycalculating thermal fatigue and damage degree based on cumulative damagerules for the member whose life is to be assessed, for preparing anapproximate expression of the relationship between the estimationparameter and the thermal fatigue and damage degree; means for promptinga terminal connected through a network to input the start count of themember whose life is to be assessed; means for assessing the life of themember from the input start count by using the approximate expression;and means for outputting the assessed life to the terminal.
 64. Anapparatus for assessing the life of a member provided in an apparatuswhich is started and stopped over and over again and subjected to a highin-service temperature for a long period while the apparatus is beingoperated, comprising: means for using an estimation parameter which is afunction of the start count and thermal stress, and data established bycalculating thermal fatigue and damage degree based on cumulative damagerules for the member whose life is to be assessed and approximating therelationship between the estimation parameter and the thermal fatigueand damage degree and preparing an expression estimating the thermalfatigue and damage degree added with probabilistic statisticalprocessing; means for prompting a terminal connected through a networkto input the start count and the hardness of the member whose life is tobe assessed; means for assessing the life of the member from the inputstart count and hardness by using the approximate expression; and meansfor outputting the assessed life to the terminal.
 65. An apparatus forassessing the life of a member provided in an apparatus which is startedand stopped over and over again and subjected to a high in-servicetemperature for a long period while the apparatus is being operated,comprising: means for inputting the start count of the member whose lifeis to be assessed from a terminal connected to a network; and means foraccording to the input, in a service supplying equipment connected tothe network, assessing the life of the member by an approximateexpression of the relationship between the estimation parameter and thethermal fatigue and damage degree, which is approximated from anestimation parameter which is a function of the start count and thermalstress, and data established by calculating thermal fatigue and damagedegree based on cumulative damage rules for the member whose life is tobe assessed, and outputting the assessed life to the terminal.
 66. Anapparatus for assessing the life of a member provided in an apparatuswhich is started and stopped over and over again and subjected to a highin-service temperature for a long period while the apparatus is beingoperated, comprising: means for inputting the start count and hardnessof the member whose life is to be assessed from a terminal connected toa network; and means, according to the input, in a service supplyingequipment connected to the network, for using an estimation parameterwhich is a function of the start count and thermal stress, and dataestablished by calculating thermal fatigue and damage degree based oncumulative damage rules, for the member whose life is to be assessed,approximating the relationship between the estimation parameter and thethermal fatigue and damage degree, assessing the life of the member byan expression estimating the thermal fatigue and damage degree addedwith probabilistic statistical processing, and outputting the assessedlife to the terminal.
 67. A computer program utilized in a computersystem, comprising steps of performing the method defined in claim 5.68. A computer program utilized in a computer system, comprising stepsof performing the method defined in claim 18.